Authorities in the border city of Ciudad Juarez said on Tuesday night that they had arrested a man suspected of taking part in a shooting attack on a high-school party that killed at least 15 people early Sunday.
Officials summoned reporters to see the suspect, who said in their presence that the main Juarez-based drug cartel targeted the party because it had received reports that members of a rival trafficking group were in attendance.
The suspect, identified as Jose Dolores Arroyo Chavarria, said he acted as a lookout for the 24 or so gunmen he said took part. He said they were ordered to kill everyone inside.
Authorities said they arrested the suspect Monday afternoon after army troops interrupted the planned assassination of a drug rival. Killed during that gunfight was one of the men who allegedly supervised the assault on the party, in which dozens of young people packed a private home.
Officials said some of the same gunmen are believed to be responsible for the killings of four people Monday at a dance hall.
Authorities in the state of Chihuahua on Tuesday gave the number of dead as 15, though a day earlier they had said 16 died, a figure corroborated by local news reports.
Parents of the slain teens have denied that their children were involved in criminal activity.